
Background Art
Modern day aircraft and spacecraft, and particularly modern day military platforms, typically make use of a large number of optical components. Due to the physical characteristics of light, most electro-optical applications require alignment between one or more optical components. For example, the most basic function of launching light into an optical fiber requires alignment of the fiber with the light source. Typically, the light source will be a laser and the application will require high accuracy beam pointing. Such a configuration is commonly used in applications such as optical scanners, laser designators or projector systems. Another type of application involves the positioning of microlens arrays, which typically need to be moved for tens to hundreds of microns in one or two dimensions. Movement in such small proportions is termed "translation" in the optics industry and is the subject of much attention. Other applications include laser communications, laser radar and optical steering for unmanned airborne vehicles.
Conventional approaches to translating optical elements have employed piezo rod actuators to provide the required displacement. Rod actuators, however, are heavy, large, non-planar and bulky. These limitations have hindered the development of optical systems for airborne and space applications as well as other electro-optical systems requiring compactness and a large translation length. Translation length is defined by the amount of displacement achievable for a given voltage and rod length. Thus, rod actuators require a relatively large rod length for very small translation lengths. Typically, translation lengths are on the order of one micron per millimeter of rod length for applied fields of about 20 kV/cm.
Translation length is also affected by the weight of the optical element being displaced. For example, a typical lens array can weigh as little as 80 grams. This relatively small weight does not require the force generated by rod actuators. It is therefore desirable to enable relatively large displacements of lightweight optical elements at higher speeds and in very compact actuation systems.
It would further be desirable to provide a method and device for providing relatively large displacement of a micro-optic element using a small voltage. It will be appreciated that power consumption is often just as critical to optical applications as size. Accordingly, a large translation length is needed.
It would also be highly desirable to provide a method and system having inherent mechanical amplification. Such a system would allow increased compactness and lower voltages. It would also be desirable to provide high accuracy feedback to increase the speed of actuation. Conventional rod actuators are sluggish due to their size, weight and feedback problems.
It will be understood that displacement on the order of tens of microns is significantly affected by environmental effects. For example, slight fluctuations in temperature can result in changes in material properties which cause a substantial amount of system noise. It is therefore highly desirable to provide a micro-optic translation system with temperature compensated designs and/or compact and effective environmental isolation.